Recently, a waterdrop dropped on a windshield of an automotive vehicle is detected so that a windshield wiper of the vehicle is automatically operated on the basis of detection of the waterdrop. This type of wiper controller for controlling the wiper to wipe the waterdrop on the windshield automatically is well-known. Thus, a driver of the vehicle needs not to decide whether the wiper is operated, so that driving burden of the driver is reduced when the driver drives the vehicle. Specifically, the driver needs not to judge circumstance of rain. The wiper controller for controlling the wiper is disclosed in, for example, Japanese Patent Application Publication No. H9-109840.
As shown in FIG. 14, the wiper controller includes a windshield wiper 41, i.e., a wiper blade for wiping the windshield, a motor 40 as a driving portion for driving the wiper 41, a control portion 130 as control means for controlling operation of the wiper 41 through the motor 40 and determining circumference of rain, an illumination sensor 120a and a waterdrop sensor 120b. The illumination sensor 120a detects illumination of light entered from outside of the vehicle into a compartment of the vehicle through a windshield 10. The waterdrop sensor 120b detects a waterdrop W dropped, i.e., attached to the windshield 10. Detection signals from the illumination sensor 120a and the waterdrop sensor 120b are inputted into the control portion 130. When the driver selects operation of the wiper 41 by using the wiper controller through a wiper switch (not shown), the controller 130 controls to operate the wiper 41 through the motor 40 on the basis of judgment and determination by the controller 130. The illumination sensor 120a includes a louver 121 disposed in front of the sensor 120a, as shown in FIG. 15. The illumination sensor 120a detects the light having a predetermined angle θ and entered into the sensor 120a through the louver 121 so that the sensor 120a outputs a detection signal, i.e., an illumination signal XVIA corresponding to amount of the light. Here, the louver 121 selects the light to be entered into the sensor 120a with the predetermined incident angle θ.
FIG. 16 is an electric block diagram of the wiper controller. The operation of the wire controller is explained as follows with reference to FIGS. 14 to 16. Firstly, the control portion 130 determines whether the waterdrop W is attached to the windshield 10 on the basis of the waterdrop detection signal XVIB outputted from the waterdrop sensor 120b. When the control portion decides that the waterdrop W is attached to the windshield 10, the control portion 130 determines whether it is nighttime on the basis of the illumination signal XVIA outputted from the illumination sensor 120a. When the control portion 130 decides that it is nighttime, the control portion 130 determines whether the light entered from an external light source into the illumination sensor 120a is a light refracted by the waterdrop W. Specifically, as shown in FIG. 14, assuming that the light along with a light pass L is detected by the sensor 120a, firstly, the light is emitted from a light source 100 such as a street light disposed outside of the vehicle. Then, the light is refracted by the waterdrop W disposed on the windshield 10. The refracted light reaches to an eye point E of the driver. The control portion 130 determines whether amount of the light reached the eye point E is equal to or larger than a predetermined threshold amount. When the control portion 130 decides that the amount of the light is larger than the predetermined threshold amount, the control portion 130 outputs a wiper driving signal XVIC to the motor 40. Specifically, when the amount of the light is larger than the predetermined threshold amount, it is considered that the driver's view is blocked by the light reached to the eye point E of the driver. Thus, in this case, the control portion 130 operates the wiper 41 through the motor 40 so that the waterdrop is wiped, if the wiper 41 does not work. Further, when the wiper has already worked, the control portion 130 operates the wiper 41 through the motor 40 by an intermittent wiping operation having a predetermined time interval.
Thus, in the wiper controller, the operation of the wiper 41 is controlled on the basis of the amount of the light entered into the illumination sensor 120a through the windshield 10 with the predetermined angle and detected by the illumination sensor 120a. Therefore, even if the windshield 10 is water-repellent finished, the control portion 130 operates to drive the wiper 41 through the motor 40 in order to remove the waterdrop W when the vehicle runs under the nighttime street light. Thus, it is eliminated that the light is reflected diffusely by the waterdrop W. Accordingly, the driver is protected from blocking his view by the reflection of the light by the waterdrop.
However, since the wiper 41 is actively operated in order to eliminate the waterdrop reflection of the light, the operation of the wiper 41 may interrupt the driver's view. Specifically, although the wiper controller eliminates the waterdrop reflection of the light, the interruption of the operation of the wiper 41 may remain to bother the driver's view. Accordingly, there is a room for improving operation of the wiper 41 so that preferable driving conditions are obtained.